Use GreenPoison to jailbreak iOS 4.2.1
Hello guys, how are you today? Hope you are doing fine.
I am very happy today because I have just finished upgrading and jailbreaking my iPhone 3GS to iOS 4.2.1. And I am writing this article because I want to share with you on on how to jailbreak iOS 4.2.1 with GreenPoison.
Before we can start, make sure you have all the tools that we need:
- iPhone with iOS 4.2.1
- GreenPoison (current version is RC6 but I’m using RC5 in this tutorial)
Let’s do the jailbreak!
- Backup your iPhone using iTunes.
- Run GreenPoison and click on the “Prepare to Jailbreak (DFU)” button.
- Follow the instructions given by GreenPoison:
- Press and hold the sleep button for 2 seconds
- While holding Sleep button, press and hold Home button for 10 seconds
- Release the Sleep button but continue holding Home button for 15 seconds
- When your iPhone in DFU mode, click on the “Jailbreak!” button.
- Wait until GreenPoison finish jailbreaking your iPhone.
- Your iPhone will restart and you will see GreenPoison icon during boot up.
- Launch Loader icon from your Homescreen and install Cydia.
- Congratulations! You now have a jailbroken iOS 4.2.1.
I had no issues during the jailbreaking process. If you have any, please leave your comment below. I will do my best to help you jailbreaking your iOS 4.2.1 with GreenPoison. 
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